Citral

Citral, or 3,7-dimethyl-2,6-octadienal or lemonal, is either a pair, or a mixture of terpenoids with the molecular formula C10H16O. The two compounds are geometric isomers. The E-isomer is known as geranial or citral A. The Z-isomer is known as neral or citral B.

Citral[1]

Geranial

Neral
Names
IUPAC name
3,7-dimethylocta-2,6-dienal
Other names
citral
geranialdehyde
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.023.994
EC Number
  • 226-394-6
KEGG
RTECS number
  • RG5075000
UNII
UN number 2810
Properties
C10H16O
Molar mass 152.24 g/mol
Appearance Pale yellow liquid
Odor Lemon like
Density 0.893 g/cm3
Boiling point 229 °C (444 °F; 502 K)
Vapor pressure 0.22 mmHg (20 °C)
−98.9×10−6 cm3/mol
Hazards
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H315, H317
P261, P264, P272, P280, P302+352, P321, P332+313, P333+313, P362, P363, P501
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Flash point 91 °C (196 °F; 364 K)
Related compounds
Related alkenals
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Occurrence

Citral is present in the oils of several plants, including lemon myrtle (90–98%), Litsea citrata (90%), Litsea cubeba (70–85%), lemongrass (65–85%), lemon tea-tree (70–80%), Ocimum gratissimum (66.5%), Lindera citriodora (about 65%), Calypranthes parriculata (about 62%), petitgrain (36%), lemon verbena (30–35%), lemon ironbark (26%), lemon balm (11%), lime (6–9%), lemon (2–5%), and orange.[2][3][4]

Uses

Citral has a strong lemon (citrus) odor. Neral's lemon odor is less intense, but sweeter. Citral is therefore an aroma compound used in perfumery for its citrus effect. Citral is also used as a flavor and for fortifying lemon oil. It also has strong antimicrobial qualities,[5] and pheromonal effects in acari and insects.[6][7]

Citral is used in the synthesis of vitamin A, lycopene, ionone, and methylionone, to mask the smell of smoke.

Health and safety information

Two studies showed 1–1.7% of people to be allergic to citral, with allergies frequently reported. Citral on its own is strongly sensitizing to allergies; the International Fragrance Association recommends that citral only be used in association with substances that prevent a sensitizing effect. Citral has been extensively tested, with no known genotoxicity or carcinogenic effect.[8]

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See also

References
  1. Citral, The Merck Index, 12th Edition.
  2. Fenaroli, G., Furia, T.E., Bellanca, N., Handbook of Flavor Ingredients, ISBN 0-87819-532-7
  3. Lawless, J., The Illustrated Encyclopedia of Essential Oils, ISBN 1-85230-661-0
  4. The Aromatic Plant Project
  5. Onawunmi, G.O. (1989). "Evaluation of the antimicrobial activity of citral". Lett. Appl. Microbiol. 9 (3): 105–108. doi:10.1111/j.1472-765X.1989.tb00301.x.
  6. Kuwahara, Yasumasa; Suzuki, Hiroshi; Matsumoto, Katsuhiko; Wada, Yoshitake (1983). "Pheromone study on acarid mites. XI. Function of mite body as geometrical isomerization and reduction of citral (the alarm pheromone)". Applied Entomology and Zoology. 18 (1): 30–39. doi:10.1303/aez.18.30.
  7. Robacker, D.C.; Hendry, L.B. (1977). "Neral and geranial: components of the sex pheromone of the parasitic wasp, Itoplectis conquisitor". J. Chem. Ecol. 3 (5): 563–577. doi:10.1007/BF00989077.
  8. Survey and health assessment of chemical substances in massage oils Archived 28 June 2007 at the Wayback Machine

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